Ann: Sinclair Mine Complete, First Caesium Shipment Scheduled, page-40

A 2001 report which may be of interest contains the use of Caesium Formate to test coal
http://www.cabotcorp.com/~/media/fi...micals-notification-and-assessment-scheme.pdf
File No: NA/811
September 2001
NATIONAL INDUSTRIAL CHEMICALS NOTIFICATION
AND ASSESSMENT SCHEME
FULL PUBLIC REPORT
Caesium Formate
This Assessment has been compiled in accordance with the provisions of the Industrial Chemicals
(Notification and Assessment) Act 1989 (the Act) and Regulations. This legislation is an Act of the
Commonwealth of Australia. The National Industrial Chemicals Notification and Assessment
Scheme (NICNAS) is administered by the National Occupational Health and Safety Commission
which also conducts the occupational health & safety assessment. The assessment of environmental
hazard is conducted by the Department of the Environment and the assessment of public health is
conducted by the Department of Health and Aged Care.
For the purposes of subsection 78(1) of the Act, copies of this full public report may be inspected by
the public at the Library, National Occupational Health and Safety Commission, Plaza level, Alan
Woods Building, 25 Constitution Avenue, Canberra ACT 2600 between 9 AM and 5 PM Monday to
Friday.
Copies of this full public report may also be requested, free of charge, by contacting the
Administration Coordinator on the fax number below.
For enquiries please contact the Administration Section at:
Street Address: 92 -94 Parramatta Rd CAMPERDOWN NSW 2050, AUSTRALIA
Postal Address: GPO Box 58, SYDNEY NSW 2001, AUSTRALIA
Telephone: (61) (02) 9577 9514 FAX (61) (02) 9577 9465
Director
Chemicals Notification and Assessment
TABLE OF CONTENTS
FULL PUBLIC REPORT...........................................................................................................4
1. APPLICANT..................................................................................................................4
2. IDENTITY OF THE CHEMICAL.................................................................................4
3. PHYSICAL AND CHEMICAL PROPERTIES.............................................................5
3.1. Comments on Physico-Chemical Properties ..........................................................5
4. PURITY OF THE CHEMICAL.....................................................................................7
Species....................................................................................................................................7
5. USE, VOLUME AND FORMULATION......................................................................8
6. OCCUPATIONAL EXPOSURE .................................................................................10
7. PUBLIC EXPOSURE..................................................................................................11
8. ENVIRONMENTAL EXPOSURE..............................................................................12
8.1 Release .................................................................................................................12
8.2 Fate .......................................................................................................................13
9. EVALUATION OF TOXICOLOGICAL DATA.........................................................13
9.1 Acute Toxicity......................................................................................................13
9.1.1 Acute Oral Toxicity......................................................................................14
9.1.2 Dermal Toxicity ...........................................................................................15
9.1.3 Acute Inhalational Toxicity..........................................................................15
9.1.4 Skin Irritation ...............................................................................................15
9.1.5 Eye Irritation.................................................................................................16
9.1.6 Skin Sensitisation .........................................................................................17
9.2. Repeated Dose Toxicity .......................................................................................17
9.3 Genotoxicity .........................................................................................................18
9.3.1 Salmonella typhimurium Reverse Mutation Assay ......................................18
9.3.2 Chromosomal Aberration Assay in Human lymphocytes ............................18
9.4 Overall Assessment of Toxicological Data..........................................................19
10. ASSESSMENT OF ENVIRONMENTAL EFFECTS.............................................20
10.1 Freshwater Species ...............................................................................................21
10.2 Marine Species .....................................................................................................22
10.3 Summary of Aquatic Toxicity..............................................................................23
11. ASSESSMENT OF ENVIRONMENTAL HAZARD.............................................24
12. ASSESSMENT OF PUBLIC AND OCCUPATIONAL HEALTH AND SAFETY
EFFECTS .................................................................................................................25
13. RECOMMENDATIONS .........................................................................................26
13.1 Secondary notification..........................................................................................26
14. MATERIAL SAFETY DATA SHEET....................................................................27
15. REFERENCES.........................................................................................................27
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NA/811
FULL PUBLIC REPORT
Caesium Formate
1. APPLICANT
Central Chemical Consulting Ltd of 7 Silica Road, Carine 6020, West Australia and Cabot
Australasia of 300 Millers Road, Altona, Victoria, 3018 have submitted a joint standard
notification statement in support of their application for an assessment certificate for caesium
formate.
2. IDENTITY OF THE CHEMICAL
The notified chemical is derived from salt mineral deposits in Canada, which also have high
levels of magnesium, calcium and other bivalent metals. These are removed through
precipitation of their carbonates, and this accounts for the relatively high level of potassium
carbonate in the notified chemical. The high levels of alkali metals (sodium, potassium and
rubidium) in the product are in accord with its origin in lake salt deposits.
Chemical Name: Caesium formate
Chemical Abstracts Service
(CAS) Registry No.:
3495-36-1
Other Names: Formic acid, caesium salt
Marketing Name: caesium formate solution
caesium formate brine
Molecular Formula: CsCHO2
Structural Formula:
O
C
O
H
- Cs
+
MolecularWeight: 177.94
Method of Detection
and Determination:
Infrared (IR)
Spectral Data: IR spectrum: 3422 (water), 2805, 1631, 1593, 1383,
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1349, and 762 cm -1
3. PHYSICAL AND CHEMICAL PROPERTIES
The following data refer to a stock solution of caesium formate (72 wt %) in water.
Appearance at 20 °C & 101.3 kPa: colourless to very pale yellow solution with a mild
odour
Boiling Point: 110°C (solution decomposes above 190°C)
Density: 2320 kg/m3 (saturated solution)
Vapour Pressure: 0.466 kPa at 20oC, 0.732 kPa at 25oC – see comments
below
Water Solubility: 4.88 g of CsHCO2 dissolve in 1 g water at 20oC;
(density = 2.3 g/mL) – see comments below
Partition Co-efficient
(n-octanol/water): log Kow < -1.28 – see comments below
Hydrolysis as a Function of pH: stable to hydrolysis at pH 4, 7 and 9; Method OECD
TG 111 – see comments below.
Adsorption/Desorption: log Koc = 1.87-2.93. Method OECD TG 106 – see
comments below.
Dissociation Constant: pKa = 3.74 ± 0.06; Method OECD TG 112 – see
comments below
Flash Point: not applicable
Flammability Limits: not flammable; combustible
Autoignition Temperature: not determined
Explosive Properties: not expected to be explosive
Reactivity/Stability: stable up to 190°C; classed as a mild reducing agent,
which when in contact with oxidants, can react
vigorously
3.1. Comments on Physico-Chemical Properties
The boiling point of concentrated aqueous salt solutions is significantly elevated above that of
water, and the measured value is in keeping with this. The notifier also indicated that the
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solution decomposes above 190oC, and this presumably refers to decomposition of the formate
anion to form CO2 and hydroxide ion.
The report on determination of vapour pressure indicated that the melting point of the solution
should be 17oC, but that the commercial solution remained supersaturated down to 1oC. This
may be due to the presence of relatively high concentrations of other ionic salt impurities which
stabilise the solution in the metastable supersaturated state.
The vapour pressure of the commercial solution was determined (Pelletier, 1998) between 1
and 39oC using a calibrated pressure transducer and, for those temperatures between 17 and
39oC, the data provided a linear relationship between pressure and reciprocal temperature
(degrees K).
Caesium formate is highly water soluble and a saturated solution at 20oC containing 4.88 kg of
solid CsHCO2 in 1 L of water has a volume of 2.56 L and a density of 2.297 kg/L.
Hydrolysis of the notified chemical was examined as a function of solution pH (Gibb and
Benton, 1998a) using a 0.08 M solution held for 5 days at 50oC in buffer solutions of pH 4, 7
and 9. After the 5 day period, the concentration of formate in the solutions was analysed using
High Performance Liquid Chromatography (HPLC), and compared with that in controls held at
5oC in a refrigerator. No significant decrease in formate concentration was observed between
any of the test solutions and the controls, with the maximum decrease recorded being 2.3 %.
These results indicate insignificant hydrolytic degradation at 50oC under the test conditions, and
even less degradation is expected at ambient temperatures.
The n-octanol/water partition coefficient of ionic materials such as caesium formate is expected
to be low due to the very high affinity for the aqueous phase. The partition coefficient was
determined (Boeri et al., 1997) through direct measurement of the caesium formate
concentration in water and n-octanol after an aqueous solution containing 0.00075 mol/L (133.4
mg/L) of CsHCO2 was equilibrated for 6 hours at 25oC with water saturated n-octanol at
volume ratios 1:5, 1:10 and 1:20 (water: n-octanol). Analysis was performed using HPLC, and
in all three cases the concentration of caesium formate in the octanol was less than 0.000040
mol/L. The partition coefficient (Pow) was consequently determined as < 0.0533, and the
corresponding log Pow < -1.28.
A report on the adsorption and desorption of caesium formate on three soil types was submitted
(Gibb and Benton, 1998b). The three soil types used were an Aridisol, an Ultisol and an Alfisol
and are characterised by different relative contents of clay, organic matter and cation exchange
capacity (CEC).
Soil Organic Matter (%) Clay Content (%) CEC (Cmol/kg)
Aridsol 0.79 13.0 8.7
Ultisol 1.95 33.0 26.2
Alfisol 0.70 8.8 7.7
Eight grams of each soil sample was agitated for 48 hours with solutions containing known
concentrations of caesium formate, and the percent adsorption onto the soil monitored over the
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test period through analysis of the residual formate concentrations in the solution. The results
were analysed to provide a log Koc of 1.87 for the Ultisol, 2.74 for the Aridisol and 2.93 for the
Alfisol respectively. From the physico-chemical properties of the soil supplied there appeared
to be an inverse correlation between log Koc and the organic content of the soil, clay content of
the soil and cation exchange capacity of the soil. Consequently it is difficult to interpret the
apparent adsorption data with the usual soil physico-chemical parameters, but the measured log
Koc for the formate ion are moderate, and indicate that this ion may be reasonably mobile in soil
media.
However, subsequent studies on desorption of the formate from the soils with either CaCl2
solution or dilute hydrochloric acid failed to detect any formate ion in either aqueous phase, and
the formate ion may be rapidly degraded once associated with the soil.
The dissociation constant of the formate anion in 0.01 M caesium formate was determined
(Gibb and Benton, 1998c) by titration with dilute (0.2 M) HCl as 3.74.
4. PURITY OF THE CHEMICAL
Degree of Purity: > 98%
Hazardous and Non-hazardous
Impurities (> 1% by weight)
The impurities found in a 72 % w/w aqueous caesium
formate solution, and their reported concentrations, are
listed below.
Species Concentration
(ppm)
Species Concentration
(ppm)
K 6100 Si < 1
Na 5300 B 2
Rb 3200 P < 1
Li 301 Mo < 1
Al < 1 Tl 10
Ba 1 Cu < 1
Ca 1 Cr, Mn, Mg, Ni,
Pb
< 1
Fe < 1 SO4 23
Sr < 1 Cl 407
Insoluble < 100
Additives/Adjuvants:
Chemical name: water
CAS No.: 7732-18-5
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Weight percentage: variable, depending upon the required solution density
Chemical name: potassium carbonate
CAS No.: 584-08-7
Weight percentage: 2800 ppm; used to precipitate out transition metal
impurities and provide a buffering for the final solution
(to pH 10.00 ±0.5).
Chemical name: citric acid
Weight percentage: 150 ppm; added as a clarifier.
CAS No.: 77-92-9
5. USE, VOLUME AND FORMULATION
Use and Formulation
Caesium formate solution will be manufactured in Canada and imported for two uses. Some
of the notified chemical will be used in coal laboratories where is will be used to prepare
media of different densities and used to classify coal on the basis of whether the coal fractions
sink or float in the different density media. The remainder will be used as a drilling fluid in
the development of oil and natural gas wells worldwide. The notified chemical will be
imported either as a concentrated aqueous solution (72 % w/w) in 70 L drums or as a solid in
25 kg heat sealed polyethylene sacks.
Formate based drilling fluids will be formulated by mixing sodium, potassium and caesium
formates in water to achieve a clear solution with a specified density. The notified chemical
will be added either as a ca. 83 % caesium formate solution in water, or as the dry powder.
Caesium formate has been registered under the Harmonised Offshore and Chemical
Notification Format (HOCNF) developed under the Oslo and Paris Conventions for the
Prevention of Marine Pollution Programmes and Measures Committee (PARCOM) for use
as a drilling fluid in the North Sea oil field.
Coal Classification
When used in classification of coal, samples of the washed coal are immersed in solutions of
different concentrations, hence different densities, of caesium formate, and the coal classified
according to the fractions which sink or float in the different media. It was stated in the
dossier that around 15 coal testing laboratories in NSW and Queensland may use caesium
formate for classification purposes.
Typically testing is conducted on 1 kg samples of coal, and after the test the caesium formate
solution separated from the coal using filtration, and recovered for re-use. Some of the
caesium formate remains entrained with fine coal particles and otherwise adsorbed into pores
in the coal. The majority of this is removed through washing the coal with water prior to the
coal being returned to stockpiles, or possibly being sent to landfill. The wash water is
reconcentrated through evaporation to its original density, and used in subsequent testing.
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Nevertheless, despite the high level of re-use of these variable density fluids, some losses are
incurred. A typical laboratory may lose 110 L of the 72 % (specific gravity 2.14) caesium
formate solution each year. Since there may be 15 laboratories using the new chemical, this
leads to an annual loss estimate of around 1650 L, amounting to ca. 2.54 tonnes of solid
caesium formate.
Oil / Gas Drilling
Large quantities of the caesium formate solution will be used in oil/gas drilling operations on
off shore drilling platforms. In particular, the solution will be used during completion phases
of the drilling operation when breaching of the actual oil/gas reservoirs occurs. During
drilling operations, a drilling fluid (often also called “drilling mud” is pumped down the drill
shaft and functions as a lubricant for the drills, and also acts as a carrier fluid for removing
the solid cuttings (i.e. the rock removed from the bore hole). The drilling fluid must possess
certain density and rheological properties to function effectively under the conditions
encountered in wells, and conventionally such fluids are prepared from oil based products
supplemented with barium sulphate (as a weighting agent) and other organic additives. In
certain circumstances, the use of aqueous caesium formate solutions (whose density can be
adjusted through dilution with water) dispenses with large scale use of organic materials and
barium sulphate in this role. This lessens potential release of organic material to the
environment, and is also claimed to offer other practical engineering advantages during well
drilling (Howard, 1995).
During the development of a well, the drilling fluid is pumped down the centre of the
(hollow) drilling rods and is extruded through holes in the cutting head, which is of larger
bore than the shaft of drill rods. The fluid then fills the annular region between the bore hole
(typically 21.6 cm to 31.1 cm in diameter – see Cobby and Craddock, 1999) and the drilling
shaft, and as it is pushed back towards the surface and carries the drill cuttings with it. The
bore hole is cased and fitted with appropriate valves and plumbing to allow for the return of
the fluid and cuttings back to the drilling platform or drilling rig. Here the solid cuttings are
separated from the fluid through a series of shaker tables, centrifugation and filtration units so
that, apart from operational losses, the drilling fluid is contained within a closed loop.
The cuttings are then automatically dumped overboard, while the fluid itself is returned to the
storage tank for reuse. It is usual that on off shore drilling platforms the tailings (cuttings) are
discharged through a pipe set a little below the sea surface, but far above the sea floor.
In the submission, the company indicated that the discarded drill cuttings may contain up to
15 % (w/w) of the drilling fluid, although when centrifugation is employed this may be
dramatically reduced, and residual fluid levels as low as 1 % have been recorded. It was not
indicated in the notification whether centrifugation will be used on the North West shelf
operations but, regardless of the efficiency of the recovery operations employed, some fluid
will be ultimately discharged overboard with the drill cuttings and enter the marine
environment.
The percentage of drilling fluid recovered as described above was not indicated but, due to
the anticipated high cost of the caesium formate solution, is expected to be high. The notifier
included a copy of a detailed Loss Management Manual for the use of drill rig operators and
personnel involved in transporting and transferring the chemical to the drilling platforms.
However the company has not specified the recovery technologies to be used on Australian
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drilling platforms, or expected quantities of the notified chemical likely to be released with
discarded drill cuttings. Accordingly, for the purposes of this report it will be assumed that
discarded cuttings will contain 10 % by weight of entrained drilling fluid.
The quantity of drilling fluid used in drilling the wells is variable (depends on drill well depth
and location), but the notifier stated that a typical oil/gas drilling platform may use 1500
barrels of the notified chemical (around 160 tonnes of solid caesium formate) during drilling
each new well. The company indicated that up to four wells may be drilled each year using
the new caesium formate based fluids, and so in excess of 600 tonnes of the chemical may be
in use at any one time.
Volume
It is anticipated that up to 2250 tonnes per annum will be imported for all uses. The company
indicated that up to 3 tonnes of the notified chemical would be imported for coal sink use in
the first year, and that subsequent imports of 1 tonne per annum could be anticipated in order
to replenish losses. However, this may be conservative and, from indicative losses given in
the notification, the required replenishment quantities appear to be closer to 2.5 tonnes per
annum.
The major use for the chemical will be in oil/gas drilling on off shore drilling platforms, and
here the notifier indicated that a typical well may use up to 1500 drums (10500 L) of the 72 %
caesium formate solution which equates to the use of ca. 162 tonnes of solid caesium
formate. Since it is likely that stockpile of material sufficient for developing at least two wells
would be kept in Australia at any time, likely annual imports of caesium formate for this
purpose may exceed 300 tonnes. Every attempt is made to recover and reuse the drilling fluid
after completion of the well, but some losses are inevitable and will require replacement
through import of replacement stocks.
6. OCCUPATIONAL EXPOSURE
Transport and Storage
Estimates of the numbers of workers involved in these activities were not provided. No
exposure of workers involved in transport or storage of drums of caesium formate solution or
sacks of dry powder is expected except in the case of an accident involving damage to the
packaging. Due to the hygroscopic nature of the notified chemical, storage will always be in
enclosed, airtight packaging.
Coal Classication
Approximately 3 people in each of four coal laboratories will use caesium formate at one
time. Coal samples will be placed in caesium formate solutions of specified density manually.
The grains which float are removed, the excess solution is drained off and the grains which
sank are placed in a solution of higher density. Once the coal has been separated into its
density fractions, the coal fractions are thoroughly washed with water to remove any residual
formate. The washed coal is then oven dried. All formate washings are collected and reconcentrated
to the original density (2.14 g/L) by water evaporation.
Dermal exposure to the notified chemical in aqueous solution may occur at a number of
points during this process. There is also the possibility of splashing resulting in ocular
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contact. The notifier stated that laboratory staff will be required to wear goggles and rubber or
nitrile gloves during these activities. As the notified chemical is hygroscopic, spills will not
dry to produce dust.
Oil / Gas Drilling
During the use of caesium formate as a drilling and completion fluid, the total number of
industry persons who will be exposed to the caesium formate during the period of its initial
testing will be less than 200 persons worldwide. The team involved in drilling generally
includes a person who directs the overall operations on behalf of the operator, the drilling
superintendent who directs the day to day operations, drillers, toolpushers, roustabouts and
fluid people. The fluids team involve at least two people who mix, test and control the
drilling fluid properties while drilling operations are in progress. There will also be use of the
notified chemical solution by the completion team. The activities of the completion team
were not specified by the notifier, but are expected to involve similar exposure scenarios for
the notified chemical. All workers will be experienced personnel trained in the handling,
mixing and application of such drilling fluids, either in laboratory settings or in field
applications for drilling and completing oil and gas wells.
The notified chemical will be used by drilling contractors in closed-loop systems at the
wellhead therefore worker exposure to the caesium formate solution will be restricted to
exposure to drips and spills when the notified chemical solution is decanted or pumped from
the importation drum into the enclosed drilling system. There may also be exposure during
sampling of the fluid for testing of viscosity or other properties, and when the fluid is
transferred for storage during recovery operations. When dry powder is used to prepare the
drilling fluids, it will dissolve rapidly into drilling fluid formulations. Any dusts are expected
to absorb water from the atmosphere and minimal exposure to the dry powder form of the
notified chemical is therefore expected. There may be exposure of workers to significant
volumes of the notified chemical when the drill bit is manipulated during replacement or
removal from the drill hole. No worker exposure is anticipated during transfer of the notified
chemical from storage to the drilling site or during storage on a drilling rig.
The protection measures used to prevent exposure of these workers were not specified by the
notifier, however the Material Safety Data Sheet (MSDS) for the notified chemical indicates
that appropriate clothing, gloves and eye protection (goggles or face shield) should be worn.
The workers involved in testing, mixing and application of fluids are generally petroleum
engineers with specific skills and training in the design and application of drilling and
completion fluids.
7. PUBLIC EXPOSURE
It is expected that during transport, formulation, storage, and use, exposure of the public to
the notified chemical will be low.
Given that the use of the notified chemical will be restricted to coal testing laboratories and
onshore/offshore drilling operations, no public exposure is anticipated except in the event of
an accidental spill during transport from the docks to the drilling sites and coal testing
laboratories.
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8. ENVIRONMENTAL EXPOSURE
8.1 Release
Coal Classication
Approximately 2.5 tonnes of caesium formate may be released each year from use of the
notified chemical in coal classification laboratories, primarily in NSW and Queensland. Most
of this material will be associated with the coal samples used for the tests, with the bulk
returned to coal stockpiles for sale. Once the coal is burnt, the caesium component will be
associated with the ash which would most probably be placed into a landfill. The caesium
would most likely be in the form of soluble salts such as oxides or carbonates, and would
consequently be susceptible to leaching from the landfill. However, the associated release will
be diffuse and at very low levels.
Some of the unburnt test coal containing entrained caesium formate may be placed into
landfill, but the likely quantity was not specified. The fate of any entrained caesium formate
would be similar to that for the coal ash.
Oil / Gas Drilling
Much of the notified chemical used in drilling fluids (or muds) is expected to be released with
the waste drill cuttings to the marine environment. While no quantitative estimates or
examples of these releases were provided in the notification it will be assumed that the drill
cuttings contain up to 10 % of the new chemical. The tailings are discharged through a pipe
just below the surface and, once discharged from the drilling rig, it is expected that the solid
drill cuttings coated with residual drilling fluid would eventually settle to the sea floor.
However, depending on factors such as particle size, sea conditions, weather conditions and
ocean currents, the deposition may take some time. Also, it is likely that the distribution
would be disperse, and that the discarded cuttings would be spread over a wide area of the sea
floor.
Caesium formate solution will be used for development of the wells near the vicinity of the
reservoirs, ie drilling holes from the main well shaft into the rock formations which actually
contain the oil and gas. No information on the length, diameter and number of such
development holes for any given well was provided in the notification, but it will be assumed
that the waste generated is equivalent to that of the major well drilling operation. On a typical
production drilling platform, each bore hole may be between 1 and 4 km in length. Given that
the typical diameter of a production hole is 31.1 cm, it is estimated that each well may
produce between 75 and 300 m3 of rock cuttings with a weight of approximately 150-600
tonnes. Assuming that the cuttings contain 10 % of drilling fluid, each well may be
responsible for release of up to 60 tonnes of the drilling fluid containing an estimated 42
tonnes of caesium formate. Since caesium formate brines may be used in drilling up to four
wells each year, an annual release of around 170 tonnes of caesium formate is anticipated, ie
around 130 tonnes of caesium.
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8.2 Fate
Coal Classification
When the coal containing residual material is burnt, the formate component of the notified
chemical will be destroyed (producing CO2 and water vapour), while the caesium will
become associated with the ash, probably as an oxide or carbonate. Coal ash would normally
be disposed of into landfill. It is likely that the residual caesium salts would be susceptible to
leaching as ground water percolates through these structures, consequently releasing this
element to the aquatic environment.
Drilling Fluid
It is difficult to estimate the quantity of caesium formate likely to be released to the marine
environment with well drill cuttings but, assuming four wells are drilled each year, up to 170
tonnes of caesium formate may be released each year to the marine environment in
association with discarded drill cuttings.
However, due to the high solubility of the material, the notified chemical is expected to
diffuse into the surrounding sea water and is not expected to remain adsorbed to the drill
cuttings. The formate component will be degraded through abiotic and biotic processes, while
the caesium (ca. 130 tonnes per annum) would remain in solution. Since the caesium formate
will be released in high concentration around each drilling rig, the caesium levels in the
surrounding water will be significantly elevated above ambient concentrations.
Biodegradation
The notifier provided a test report on the ready biodegradation of the chemical (Douglas and
King, 1992b) which was performed using the closed bottle procedure of OECD TG 301 D.
This test measures the decay of dissolved oxygen in a closed vessel containing the test
material (initial concentration 45 mg/L) inoculated with sewage bacteria over a 28 day period.
The results indicated that 83 % of the test compound had degraded after 28 days, and also
since 60 % degradation had occurred within 10 days of the 10 % degradation point being
reached, the notified chemical passes the criteria for ready biodegradability. In a parallel study
using sodium benzoate, this reference compound was degraded 92 % after 28 days, which
indicates that the bacterial culture used in the test was viable.
Only the formate anion component of the notified chemical is degraded, and the caesium will
be unaffected by bacterial action.
Bioaccumulation
The highly soluble nature of the notified chemical, together with its biodegradability,
indicates that it is not likely to have significant potential for bioaccumulation.
9. EVALUATION OF TOXICOLOGICAL DATA
9.1 Acute Toxicity
A number of toxicological studies have been carried out on the notified chemical, however
data supporting some of these tests were not available. Some data reported is given as a
summary originating from internal Shell reports undertaken in 1994.
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Summary of the acute toxicity of caesium formate solution (83 %)
Test Species Outcome Reference
acute oral toxicity rat LD50 = 1780 mg/kg (Harrod (1997a)
acute dermal toxicity
(summary)
rat LD50 > 2000 mg/kg (Shell, 1994)
skin irritation rabbit slight irritant (Harrod, 1997b)
eye irritation rabbit moderate irritant (Harrod, 1997c)
skin sensitisation
(summary)
rabbit non-sensitiser (Shell, 1994)
9.1.1 Acute Oral Toxicity (Harrod, 1997a)
Species/strain: rat/Sprague-Dawley
Number/sex of animals: 5/sex/dose
Observation period: 14 days
Method of administration: gavage; 1250, 1580, 2000 and 5000 mg/kg
Test method: OECD TG 401
Mortality: all animals at 5000 mg/kg and 9/10 animals at 2000 mg/kg
died within the first day after treatment
Clinical observations: animals at dose levels of 1580 mg/kg and above exhibited
varying degrees of depression, convulsions, respiratory
distress, ataxia, excessive salivation, masticatory movements
and gross signs of distress and external staining; faecal stains
were noted at the 1250 mg/kg dose level
all surviving animals exhibited body weight gain at day 14
Morphological findings: gross necropsy findings for animals that died during the
observation period included those generally seen in agonal
animals, with indications of gastro-intestinal irritation and
external staining; there were no gross pathological changes
observed in animals which survived the 14 day observation
period
LD50: 1780 mg/kg
Result: the notified chemical was of low acute oral toxicity in rats.
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9.1.2 Dermal Toxicity
No test reports concerning the acute dermal toxicity of the notified chemical were submitted.
A summary of toxicology testing on the notified chemical (Shell, 1994) included data on
dermal toxicity testing. Doses of 50, 400 and 2000 mg/kg were administered to groups of 2
male and 2 female rats. Sites of application showed erythema on day 2, or on days 2 and 3.
The acute dermal toxicity of caesium formate monohydrate was greater than 2000 mg/kg.
9.1.3 Acute Inhalational Toxicity
No test reports were submitted.
9.1.4 Skin Irritation (Harrod, 1997b)
Species/strain: rabbit/New Zealand White
Number/sex of animals: 3/sex
Observation period: 7 days
Method of administration: 500 μL of undiluted caesium formate was applied by a
closed patch method to intact skin for 4 hrs
Test method: OECD TG 404
Draize scores:
Time after Animal #
treatment
(days)
1♂ 2♂ 3♂ 4♀ 5♀ 6♀
Erythema
1 hour 2a 2 2 1 2 1
1 1 1 1 1 2 1
2 1 1 0 1 1 1
3 1 0 0 1 1 0
7 0 0 0
Oedema
1 hour 2 2 1 1 2 2
1 1 1 0 0 1 1
2 1 1 0 0 1 0
3 1 0 0 0 1 0
7 0 0 0
a see Attachment 1 for Draize scales
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Comment: partial recovery in three animals and full recovery in three
animals were noted at 72 hours; full recovery was noted in
the remaining animals by day 7; two animals showed
desquamation at day 7; the Primary Irritation Index was
calculated to be 1.8
Result: the notified chemical was a slight irritant to the skin of
rabbits.
9.1.5 Eye Irritation (Harrod, 1997c)
Species/strain: rabbit/New Zealand White
Number/sex of animals: 3/sex
Observation period: 14 days
Method of administration: 100 μL undiluted caesium formate delivered into the right
eye of each animal
Test method: OECD TG 405
Draize scores of unirrigated eyes:
Time after instillation
Animal 1 hour 1 day 2 days 3 days
Cornea all Draize scores were zero
Iris
1♂ 1 0 0 0
2♂ 1 0 0 0
3♂ 1 0 0 0
4♀ 1 0 0 0
5♀ 1 0 0 0
6♀ 1 0 0 0
Conjunctiva r c d r c d r c d r c d
1♂ 1a 2 3 2a 2 2 2a 1 0 2a 1 0
2♂ 2a 3 3 2a 2 3 2a 2 1 2a 1 0
3♂ 1a 2 2 2a 2 2 2a 1 0 1 1 0
4♀ 1a 2 3 2a 2 2 2a 2 0 2a 1 0
5♀ 1a 2 3 2a 2 1 2a 2 1 2a 1 0
6♀ 2a 2 3 2a 2 1 2a 2 0 2a 1 0
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Time after instillation
Animal 4 days 7 days 14 days
Conjunctiva r c d r c d r c d
1♂ 2a 1 0 1 1 0 0 0 0
2♂ 1a 1 0 1a 1 0 0 0 0
3♂ 1 1 0 0 0 0
4♀ 1a 1 0 1a 1 0 0 0 0
5♀ 1a 1 0 1a 1 0 0 0 0
6♀ 1a 1 0 1a 1 0 0 0 0
1 see Attachment 1 for Draize scales
r = redness c = chemosis d = discharge
a = one or more of the additional observations discussed below were also reported
Comment: iritis in all animals cleared by 24 hours; no corneal opacity
was observed
additional observations included a blistered appearance to
the conjunctiva or nictitating membrane, areas of
conjunctiva or nictitating membrane appeared haemorrhagic,
and areas of nictitating membrane appeared blanched
Result: the notified chemical was moderately irritating to the eyes of
rabbits.
9.1.6 Skin Sensitisation
No test reports concerning the skin sensitizing potential of the notified chemical were
submitted. A summary of toxicology testing on the notified chemical (Shell, 1994) included
data on a Buehler test with induction and challenge by occluded topical application of 80 %
w/v caesium formate in water. None of the 20 test animals showed any overt reaction to
treatment.
9.2. Repeated Dose Toxicity
Repeated dose toxicity data for caesium formate were not available. The subchronic effects of
the notified chemical are expected to be those of the constituent parts, the formate anion and
the caesium cation. In the stomach, these are likely to be in the form of formic acid and
caesium chloride, respectively.
Formic acid did not demonstrate any significant toxicity in rats when administered in their
drinking water 4 (0.5% and 1.0%) for 2 to 27 weeks (Sollman, 1921). In a 6 week test in rats,
the same doses are reported to have resulted in reduction in organ weights and body weight
gain (Gangolli, 1999). The caesium cation is reported to be of higher toxicity than Na+, but
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lower toxicity than K+, Li+ or Rb+ (Burt, 1986). It is further stated by Burt that the toxicology
of caesium compounds results from the anion rather than the caesium cation.
9.3 Genotoxicity
9.3.1 Salmonella typhimurium Reverse Mutation Assay
No test reports concerning the genotoxicity of the notified chemical were submitted. A
summary of toxicology testing on the notified chemical (Shell, 1994) included data on a point
mutation test. The notified chemical was not mutagenic in both the presence and absence of
liver S-9 fraction in two strains. The tests were not performed in duplicate.
9.3.2 Chromosomal Aberration Assay in Human lymphocytes (Akhurst, 1995)
Cells: human lymphocytes
Metabolic activation
system:
S-9 mix (rat liver)
Dosing schedule: 625, 1250, 2500 and 5000 μg/mL
Metabolic
Activation
Experiment/
Study Number
Test concentration (μg/mL) Controls
1 treatment time = 18 hour harvest
(625, 1250 and 2500 μg/mL)
2 treatment time = 18 hour harvest
(625, 1250 and 2500 μg/mL)
-S9
treatment time = 32 hour harvest
(1250 μg/mL)
Positive: EMS
Negative: DMSO
1 treatment time = 18 hour harvest
(625, 2500 and 5000 μg/mL)
2 treatment time = 18 hour harvest
(625, 2500 and 5000 μg/mL)
+S9
treatment time = 32 hour harvest
(500 μg/mL)
Positive: CP
Negative: water
EMS - ethyl methanesulphonate ; CP - cyclophosphamide ; DMSO – dimethylsulphoxide; - cultures selected
for metaphase analysis
Test method: OECD TG 473
Comment: no precipitation was observed; without S9 activation, the
notified chemical was cytotoxic at 5000 μg/plate; slight
toxicity was observed at this dose with S9 metabolic
activation
the notified chemical caused no substantial increase in the
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proportion of metaphase cells containing chromosomal
aberrations at any dose level when compared with the
solvent control
in the absence of metabolic activation, there was a
statistically significant increase in the proportion of aberrant
cells at 2500 μg/mL, 18 hour harvest in the second test,
however the proportion was marginally above the historical
control value and no similar increase was observed in the
first test
all positive control compounds caused large, statistically
significant increases in the proportion of aberrant cells
Result: the notified chemical was non clastogenic under the
conditions of the test
9.4 Overall Assessment of Toxicological Data
Caesium formate solution (83%) had low acute oral toxicity in rats (LD50 = 1780 mg/kg),
with clinical signs including depression, convulsions, respiratory distress, ataxia, excessive
salivation, masticatory movements, and signs of distress and external staining at > 1250
mg/kg, faecal stains were, evident at 1250 mg/kg. Caesium formate solution (83 %) was a
slight skin irritant and a moderate eye irritant. In the eye irritation study, iritis was seen in all
rabbits at 1 hour, with resolution at 24 hours. Conjunctival erythema and oedema occurred in
all rabbits from 1 hour to 7 days after instillation. Conjunctival chemosis was evident in all
rabbits at 1 to 48 hours after instillation. Some or all of the following observations occurred
in all rabbits from 1 hour up to 7 days after instillation; blistering of the conjunctiva,
blanching and/or blistering of the nictitating membrane, and haemorrhagic areas in the
conjunctiva and/or nictitating membrane, All signs of irritation had cleared by day 14.
Summaries of experimental findings were submitted for the following endpoints. Caesium
formate monohydrate had low dermal (LD50 >2000 mg/kg) toxicity in rats, with signs of
erythema, noted at sites of application on days 2 and 3. Aqueous Caesium formate (80 % w/v)
was not sensitising to guinea pigs in a Buehler test. An acute inhalation study was not
submitted.